Field
The present disclosure relates generally to radio-frequency (RF) generators and, more specifically, to apparatuses and techniques for tuning the frequency of an RF generator that supplies power to a plasma processing chamber to change the impedance of the plasma load in a desired manner.
Background
In plasma processing, a radio-frequency (RF) generator is used to supply power to the plasma load. Today's advanced plasma processes include ever more complicated recipes and recipe-changing procedures in which load (plasma) impedance dynamically changes. This can make it challenging to match the source impedance of the RF generator with the load impedance of the plasma for efficient power transfer. Such impedance matching can be performed using a matching network, but this approach is relatively slow in the context of modern short-duration plasma processes. An alternative approach is to adjust the frequency of the RF generator, which alters the impedance of the plasma load. “Plasma load,” in this context, includes the plasma itself and any matching network. Such an approach has the potential to be much faster than adjusting a matching network. It is also possible to combine the two techniques (one or more matching networks and frequency tuning).
Conventional frequency-tuning algorithms struggle with optimizing parameters for these advanced plasma processes because both frequency stability and rapid frequency tuning are required simultaneously. There is, therefore, a need in the art for an improved apparatus for frequency tuning in an RF generator.